Remarkable Ebola recovery rate in north Guinea town puzzles experts

Health workers take blood samples for Ebola virus testing at a screening tent in the local government hospital in Kenema, Sierra Leone, June 30, 2014. REUTERS/Tommy Trenchard

DAKAR (Thomson Reuters Foundation) – Three quarters of those suffering from the deadly Ebola virus in a small town in northern Guinea have recovered, an unusually high proportion that is puzzling scientists and aid workers.

The medical charity Medecins Sans Frontieres (MSF) says that 16 of the 21 people suffering from Ebola who entered its treatment centre in Telimele made a full recovery, compared with only 20-40 percent of victims in Gueckedou, the epicentre of the virus in southern Guinea.

The outbreak of Ebola in Guinea, Liberia and Sierra Leone is the largest ever, according to the World Health Organization (WHO), which has reported 518 deaths from 844 known cases since February.

MSF said it had closed its treatment centre in Telimele because no new cases had been reported for 21 days – the maximum incubation period for Ebola.

The WHO said that 10 Ebola sufferers had died in Telimele out of 26 cases, the difference from the MSF figures being due to the fact that the five extra cases had not been treated at the MSF centre.

Experts are now trying to work out whether the high recovery rate in the town – where the sample size was very small - was due to genetics, culture, more effective aid, a viral mutation, or faulty laboratory tests.

Michel Van Herp, who has been working on Ebola for MSF all over Africa for the last 20 years, told Thomson Reuters Foundation the figures in Telimele are very surprising, but there may be rational explanations.

“It could be that the people in the north have a different cultural way of taking care of their dead, which may result in a lower viral load, so less virus enters the body than from funeral practices in the south,” he said. In Guinea, relatives stroke the body of the dead person as part of their mourning ritual.

“It could also be down to genetics. In Telimele there is one man who has 12 wives, so he may have disbursed his [Ebola-resistant] chromosome around all the families there,” Van Herp said.

There is no known cure for Ebola, whose victims show symptoms like those of influenza before progressing to massive internal and external bleeding. Palliative treatment has been shown to increase the chance of survival by around 10 percent.

“The (Telimele) clinic is in the centre of town, visible and easily accessible. We have a very good relationship with the local people here who are helping us to find victims early and provide them with treatment,” Van Herp said.

VIRAL MUTATION, FALSE POSITIVES

A foreign laboratory expert familiar with the West Africa Ebola outbreak said the dramatic drop in the number of deaths in Telimele and some other regions could be due to immunological causes, a mutation of the virus or false-positive laboratory results.

“The observed differences in the survival rate of some Ebola patients might be due to a mutation of the original virus, a natural increased immunity in the respective population or methodological differences between different lab tests,” said the expert, who wished to remain anonymous.

Of these, faulty lab tests are the most likely reason, he said.

Both the European Mobile Laboratory and the Pasteur Institute have been involved in the blood analysis for testing Ebola patients in Guinea, but they have been using different techniques, resulting in a debate on how false positives could have appeared.

A ‘false positive’ lab result means that a suspected Ebola victim is diagnosed as having the disease when in fact he does not. His ‘recovery’ then distorts the statistics, especially in a small sample, as in Telimele.

“Conducting molecular diagnostics for Ebola virus is technically challenging, especially under limited conditions in the field. As the technology is highly sensitive, the prevention of cross-contamination from a positive patient sample to a negative patient is an important issue for all lab teams,” the expert said.

Sakoba Keita of the Guinean Health Ministry told Thomson Reuters Foundation there had been cases of false positives in Guinea, but declined to comment on individual laboratories’ performance.

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